1. Field of the Invention
The present invention relates to a lens barrel to hold a plurality of lenses, in particular to one to facilitate the axis alignment of lenses.
2. Description of the Prior Art
In recent years there has been a continuous demanding for an imaging device such as a camera to downsize and improve image quality. To improve image quality, the number of lenses has been increased and to downsize the imaging device, a lens barrel configured to collapse the lenses into a camera housing at non-photographing and protrude them at photographing has been developed. It is necessary to precisely align the optical axes of lenses at a predetermined position in accordance with the setting of an optical system in a direction orthogonal to the optical axis of the optical system. Japanese Patent Application Publication No. 2008-111932 discloses a lens barrel in which the optical axes of lenses are precisely aligned in a direction orthogonal to the optical axis of the lenses for the purpose of align the optical axes of whole or part of the optical system, for example.
This lens barrel is configured that a first cylindrical lens frame holding a first lens includes a concave portion and a second cylindrical lens frame holding second and third lenses is fitted into the concave portion. The concave portion is formed around the first lens frame to fit into the second lens frame with a predetermined gap. In this lens barrel the optical axis of the second lens can be aligned with that of the first lens by fitting the second lens frame holding the second lens into the concave portion of the first lens frame holding the first lens, two-dimensionally adjusting it in a minute amount in a direction orthogonal to the optical axis with a certain aligning device and filling the gap with an adhesive at the adjusted position to fix the second lens frame. Thus, axis alignment can be easily done by a simple process of aligning one lens with the other.
However, the conventional lens barrel as above requires the use of an axis aligning device of a precise, complex structure to precisely align the axes of lenses to fix them at the aligned position with an adhesive. Because of this, in reality it is extremely difficult to properly maintain the aligned positions for fixation and align the optical axes of the lenses with precision.